Insulation

Insulation Problems

Ive heard about crawl space encapsulation, am I better off sealing the vents?

Ive heard about crawl space encapsulation. Am I better off sealing the vents to my crawl with a rigid foam board or insulating between my floor joists and keeping the space ventilated?

If you have or want a non ventilated sealed crawl space, full encapsulation, then you probably dont need to add floor insulation. Traditionally, crawl spaces have been vented to prevent problems with moisture. However there are a growing number of building professionals that recognize the benefits of a moisture controlled unventilated crawl space.

There are two main reasons for this line of thinking:

Ventilation in the winter makes it difficult to keep crawl spaces warm.

Warm, moist air brought into the crawl space through foundation vents in the summer is often unable to dehumidify a crawl space. In fact, this moist outdoor air can lead to increased moisture levels in the crawl space. This information is from US Dept of Energy website.

For a more complete discussion on encapsulated crawl spaces please see our section on crawl spaces in this website.